Shells of Pacific white shrimp (Litopenaeus vannamei), obtained from the Sea wealth frozen food Co., Ltd., Songkhla province, Thailand, were transported to the Department of Food Technology, Prince of Songkla University, Hat Yai, Songkhla within 2 h. Upon arrival, the samples were washed with tap water, followed by drying in hot air oven (Binder FED115, Tuttlingen, Germany) for 6 h at 65 °C. The dried samples were then ground to obtain the particle size of 1.0–2.0 mm. Ground shells were placed in polyethylene bag and kept in dark.